Chronic neuropathic pain is a potentially disabling condition resulting from disease or injury to the nervous system which can cause severe physical, emotional, and economic stresses to those afflicted and their family. It is well acknowledged that nerve damage causes global changes in gene expression in pain pathways, which is believed to lead to long-lasting changes in pain sensitivity and development of chronic pain. Unfortunately, however, little is known concerning how these changes are induced and regulated in response to nerve injury. The long-term goal of this research project is to understand the fundamental mechanisms of gene regulation involved in the development and maintenance of neuropathic pain. It is expected that such information can be used to identify novel targets for treatment of chronic pain and reduce the burdens and disability associated with this condition. Therefore, the objective of this research proposal is to identify changes in microRNA expression associated with nerve injury and characterize the role of these microRNAs in development of neuropathic pain. MicroRNAs are a new class of non-protein-coding RNA molecules that regulate gene expression at the level of translation. They are involved in a variety of important biological processes, including nervous system plasticity. The central hypothesis for this proposed research is that nerve injury causes changes in expression of a specific set of microRNA molecules. These microRNA molecules in turn regulate the translation of multiple mRNA molecules causing the development of chronic pain. The specific aims of this project are as follows: (1) Identify microRNAs involved in chronic neuropathic pain by inducing nerve injury in rats and quantifying changes in microRNA expression in pain pathways using microarray analysis, northern blot analysis, and real time PCR analysis. The binding affinity of microRNAs to mRNAs and conservation of mRNA sequences among different species will then be used as a means of identifying pain- related genes which may be regulated by these microRNAs at the translational level. (2) Characterize the expression patterns of the microRNAs responsive to nerve injury in the dorsal root ganglion and spinal cord using in situ hybridization. This research proposal is directly relevant to public health because the results of this study will enhance the overall understanding of chronic pain, a condition which affects people the world over. Furthermore, this project is novel in the pain field because the involvement of microRNAs in chronic pain has yet to be examined. Thus, results of this study may identify a completely new set of targets for managing pain. [unreadable] [unreadable] [unreadable]